This project is designed to understand the role of hormones and growth factors in normal mammary gland development and differentiation. Studies include: 1) examination of the role of epidermal growth factor and mammary gland-derived growth factors in lobulo-alveolar development of the mouse mammary gland, 2) defining the roles of estrogen and progesterone in priming the mammary tissue prior to whole organ culture to determine their effects on induction of EGF receptors, mammary gland-derived growth factor receptors and the production of growth factors by the animals, 3) examine the hormonal conditions in vitro which induce production of autocrine growth factors by normal mammary tissue and breast cancer cell lines.